Gas generator

ABSTRACT

The present invention provides a gas generator for expanding and inflating a driver&#39;s seat airbag. The gas generator comprises two ignitor device  8, 9  for burning gas generants  7  packed in combustion chambers  3, 4,  and enhancer device  10, 11  for allowing the flames from the ignitor device  8, 9  to be propagated circumferentially and radially of a housing  1.

TECHNICAL FIELD

[0001] The present invention relates to a gas generator used to expandand inflate an airbag system of a vehicle.

BACKGROUND ART

[0002] A gas generator that works to expand and inflate the airbagrapidly to protect a vehicle occupant from the impact at a car collisionis built in an airbag module mounted in a steering wheel and the like.The gas generator generates a large amount of gas rapidly by burning thegas generants by flames of ignitor device ignited by the application ofelectric power.

[0003] The conventional gas generator has the mode of expanding andinflating the airbag rapidly at any time that the car collision happens,irrespective of a seating position of a vehicle occupant (a normalseating position or an abnormal seating position such as astoop-shouldered position, etc.). This may cause the problem that whenthe vehicle occupant takes the abnormal seating position in proximity ofthe steering wheel and the like, the airbag cannot serve its originalfunction of protecting the vehicle occupant.

[0004] For solving this problem, there has been proposed and developedthe so-called soft inflation technique which is applied to the gasgenerator used for expanding and inflating the passenger's airbag. Theproposed gas generator Is so designed that an elongated cylindricalhousing is partitioned into two combustion chambers and also the gasgenerants in the respective combustion chambers are burnt independentlyof each other by the two ignitor devices. The ignitor devices are fixedto the housing at both axial ends thereof.

[0005] The ignitor devices are operated in such a time difference that,in the initial stage of inflation, the airbag is expanded and inflatedmoderately by a small amount of gas generated from a first combustionchamber and then is expanded and inflated rapidly by a large amount ofgas generated in the respective combustion chambers. This can provide acontrolled expansion and inflation of the airbag.

[0006] It is conceivable that this soft Inflation technique is appliedto the gas generator used to expand and Inflate the driver's seatairbag.

[0007] As the gas generator for the driver's seat airbag is usuallybuilt in a narrow space of the steering wheel, it is required to have ashort cylindrical housing. In addition, as the airbag is also mounted inthat narrow space of the steering wheel, the airbag is required so as tocover the housing of the gas generator at one axial end thereof. Forthis reason, the gas generator for the driver's seat airbag adopts thestructure that the ignitor device is mounted in the housing at the otheraxial end thereof to be in the opposite side to the airbag.

[0008] As a result of this, when the soft inflation technique is appliedto the gas generator for the driver's seat airbag, the gas generator forthe driver's seat airbag adopts the structure that the housing ispartitioned into two combustion chambers and also two ignitor devicesare mounted in the housing at the other axial end thereof. In thisstructure, when the ignitor devices are energized to ignite with anadequate time difference, the airbag is expanded and inflated moderatelyby a small amount of gas generated from the first combustion chamber inthe initial state of inflation and then expanded and inflated rapidly bya large amount of gas generated in the respective combustion chambers.

[0009] In the application of the soft inflation technique to the gasgenerator for the driver's seat airbag, one or two or more of theignitor devices must be offset from the axis of the housing in order tobe mounted in the housing at the other end thereof.

[0010] As a result of this, local combustion stemming from theeccentrically disposed ignitor device is produced in the combustionchamber in which the eccentrically disposed ignitor device is/arefitted. This causes possible problems that the gas cannot be uniformlygenerated all around the circumference of the housing and thus cannot beuniformly discharged into the airbag, then leading to the partialexpansion and inflation of the airbag, and as such may spoil theoriginal function of the airbag of protecting the vehicle occupant.

[0011] It is the object of the present invention to provide a gasgenerator that enables flames of the ignitor device to be propagated inthe circumferential direction and radial direction of the housing viaenhancer device, so as to instantaneously transfer the burning of thegas generants to the collective burning of the same, whereby thegenerated gas is uniformly discharged into the airbag.

DISCLOSURE OF THE INVENTION

[0012] A gas generator of the present invention (claim 1) comprises atleast one of a plurality of ignitor devices is eccentrically disposedwith respect to an axis of the housing and the enhancer devices forallowing the flame of the ignitor device disposed on the eccentricposition to be propagated circumferentially and radially of the housing.

[0013] According to the above gas generator, the combustion in thehousing broadens all over the whole of gas generants instantaneously bythe flames spouted from the each ignitor directly and the flamespropagated by the enhancer device. Consequently, there Is no partialcombustion which occurs in the vicinity of the ignitor eccentricallydisposed in the housing. The gas can be uniformly generated all over theinside of the housing.

[0014] Further in case that a plurality of ignitor devices ignite by anelectric current with very small time (hereinafter, minute time) delayamong of them, a multi-level expansion control can be provided, whereinan airbag is moderately expanded and inflated by a small amount ofgenerated gas in the initial stage and then rapidly expanded andinflated by a large amount of gas.

[0015] Another gas generator of the present invention (claim 2)comprises at least one of a plurality of ignitor devices eccentricallydisposed with respect to an axis of the housing and enhancer devices forallowing, at least, the flame of the ignitor device disposed on theeccentric position to be propagated circumferentially and radially ofthe housing. The enhancer devices burn the gas generants packed in aplurality of combustion chambers respectively and independently.

[0016] According to the above gas generator, the combustion in the eachcombustion chamber broadens all over the whole of gas generantsinstantaneously by the flames spouted from the each ignitor directly andthe flames propagated by the enhancer device. Consequently, there Is nopartial combustion which occurs in the vicinity of the ignitoreccentrically disposed in the each combustion chamber. The gas can beuniformly generated all over the inside of the housing.

[0017] In addition, in case that a plurality of ignitor devices igniteby an electric current with minute time delay among of them, amulti-level expansion control can be provided, wherein an airbag ismoderately expanded and inflated by a small amount of gas generated inone combustion chamber in the initial stage, and then rapidly expandedand inflated by a large amount of gas generated in all combustionchambers.

[0018] In the present invention, a gas generator may be adopted, whichcomprises a short cylindrical housing, a partition plate forpartitioning the interior of the housing into two upper and lowercombustion chambers, filter fitted in the respective combustionchambers, gas generants charged in the inside of the respective filters,two ignitor devices for burning the gas generants packed in thecombustion chambers respectively and two enhancer devices forpropagating the flames from the ignitor devices In the combustionchambers respectively.

[0019] Also, in the present invention, a housing may be adopted, whichhas a double cylinder structure or a single cylinder structure. In thedouble cylinder structure, top ends and bottom ends of the outercylinder and the inner cylinder are closed by two cover plates. In thesingle cylinder structure, top and bottom ends of the outer cylinder areclosed by two cover plates.

[0020] In the gas generator of the present invention (claim 3), theenhancer devices are respectively provided in the plurality ofcombustion chambers so as to extend circumferentially and radially ofthe housing, so as to be respectively in direct or Indirect contact withthe gas generants in the combustion chambers and so as to be ignited bythe flames spouted from the ignitor devices.

[0021] According to the above gas generator, the respective enhancerdevices can be ignited by the flames spouted from the ignitor device.The flames are propagated through the enhancer devices in thecircumferential direction and the radial direction of the housing andthen the gas generants in contact with the enhancer devices are burned.Thereby, the combustion in the respective combustion chambers broadensall over the whole of the gas generants instantaneously. And in thepresent invention, an enhancer device may be adopted, which is made ofenhancer agents and formed into a disk-shaped plate or a ring-shapedplate. In this case, the enhancer agents contact with the gas generantsdirectly. Also, in the present invention, another enhancer device may beadopted, in which enhancer agents are charged in an enhancing groove ofthe ring partition plate and the enhancing groove is tightly sealed soas to be integrated with enhancer agents. In this case, the enhanceragents contact with the gas generants indirectly.

[0022] In the gas generator of the present invention (claim 4), theenhancer device comprises an enhancing space opening in the combustionchamber and extending circumferentially and radially of the housing soas to be spouted the flames from the ignitor device into.

[0023] According to the above gas generator, the flames of the ignitordevice are propagated in the circumferential direction and the radialdirection of the housing along the enhancing space, whereby thecombustion in the respective combustion chambers broadens all over thewhole of the gas generants instantaneously.

[0024] In the gas generator of the present invention (claim 5), theenhancing space is closed by a cushioning member disposed in therespective combustion chambers. The cushioning member has a plurality ofenhancing holes arranged along the enhancing space so that enhancingspace can open toward the combustion chamber.

[0025] According to the above gas generator, the flames of the ignitordevice are propagated in the circumferential direction and the radialdirection of the housing along the enhancing space and spouted throughthe enhancing holes to the combustion chamber, whereby the combustion inthe respective combustion chambers broadens all over the whole of thegas generants instantaneously.

[0026] And, since the cushioning member is mounted in the eachcombustion chamber so as to close the enhancing space, the gas generantsare prevented from being powdered by vibration and entering theenhancing space.

[0027] In the gas generator of the present invention (claim 6), theenhancer device comprises enhancer agents containing auto-ignitionexplosive composition. According to the above gas generator, theenhancer device is automatically ignited by the flames and heat spoutedfrom the ignitor device and the flames are propagated in thecircumferential direction and radial direction of the housing.

[0028] A gas generator of the present invention (claim 7) comprises acylindrical housing, an ignitor device for burning the gas generants inthe housing and an enhancer device for allowing the flames from theignitor device to be propagated in the circumferential direction and theradial direction of the housing so as to burn the gas generants in thehousing.

[0029] Now, the soft inflation technique as mentioned above isadequately selected in accordance with the vehicle use pattern. Theabove gas generator (claim 7) in which the gas generants packed in thehousing can be burnt by using a single ignitor device, is not includedin the soft inflation technique. Also, the housing adopted includes notonly a single cylinder structure but also a multiple cylinder structureincluding a double cylinder structure and a triple cylinder structure.In these type of gas generator as well, there is the possibility thatthe partial combustion of the gas generants may be caused in the housingand then the airbag may be partially expanded and inflated. In view ofthis, the gas generator of the present invention (claim 7) adopts thestructure so that the flames from the ignitor device may be propagatedin the circumferential direction and the radial direction of the housingby the enhancer device.

[0030] Thereby, the combustion in the housing broadens all over thewhole of gas generants instantaneously by the flames spouted from theignitor directly and the flames propagated by the enhancer device.Therefore, the gas discharged into the airbag can be uniformed.

[0031] A gas generator of the present invention (claim 8) comprises anenhancer device provided in the combustion chamber of the cylindricalhousing so that the flames from the ignitor device may be propagatedcircumferentially and radially of the combustion chambers and so as toburn the gas generants in the combustion chamber.

[0032] Now, the soft inflation technique as mentioned above isadequately selected in accordance with the vehicle use pattern. Theabove gas generator (claim 8) in which the gas generants packed in thecombustion chamber can be burnt by using a single ignitor device, is notincluded in the soft inflation technique. Also, the housing adoptedincludes not only a single cylinder structure but also a multiplecylinder structure including a double cylinder structure and a triplecylinder structure. In these type of gas generator as well, there is thepossibility that the partial combustion of the gas generants may becaused in the housing and then the airbag may be partially expanded andinflated. In view of this, the gas generator of the present invention(claim 8) adopts the structure so that the enhancer device may beprovided in the combustion chamber and the flames from the ignitordevice may be propagated in the circumferential direction and the radialdirection of the combustion chamber by the enhancer device.

[0033] Thereby, the combustion in the combustion chamber broadens allover the whole of gas generants instantaneously by the flames spoutedfrom the ignitor directly and the flames propagated by the enhancerdevice. Therefore, the gas discharged into the airbag can be uniformed.

[0034] In the gas generator of the present invention (claim 9), theignitor device is eccentrically disposed with respect to an axis of thehousing.

[0035] According to the above gas generator, for example, even when theignitor device is eccentrically disposed with respect to an axis of thehousing, there is no partial combustion which occurs in the vicinity ofthe ignitor eccentrically disposed in the housing. And the combustionbroadens all over the whole of gas generants instantaneously.

[0036] In the gas generator of the present invention (claim 10), theenhancer device comprises enhancer agent containing auto-ignitionexplosive composition. According to the above gas generator, theenhancer device is automatically ignited by the flames and heat spoutedfrom the ignitor device, the flames are propagated circumferentially andradially of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a sectional view of a gas generator of the firstembodiment according to the present invention.

[0038]FIG. 2 is a diagram taken along arrowed line A-A of FIG. 1.

[0039]FIG. 3 is a sectional view of a gas generator of the secondembodiment according to the present invention.

[0040]FIG. 4 is a diagram taken along arrowed line B-B of FIG. 3.

[0041]FIG. 5 is a sectional view of a gas generator of the thirdembodiment according to the present invention.

[0042]FIG. 6 is a diagram taken along arrowed line C-C of FIG. 5.

[0043]FIG. 7 is a diagram taken along arrowed line E-E of FIG. 5.

[0044]FIG. 8 is a sectional view of a gas generator of the fourthembodiment according to the present invention.

[0045]FIG. 9 is a sectional view of a gas generator of the fifthembodiment according to the present invention.

[0046]FIG. 10 is a diagram taken along arrowed line F-F of PIG. 9.

[0047]FIG. 11 is a sectional view of a gas generator of the sixthembodiment according to the present invention.

[0048]FIG. 12 is a diagram taken along arrowed line G-G of FIG. 11.

[0049]FIG. 13 is a sectional view of a gas generator of the seventhembodiment according to the present invention.

[0050]FIG. 14 is a diagram taken along arrowed line H-H of FIG. 13.

[0051]FIG. 15 is a diagram taken along arrowed line I-I of FIG. 13.

[0052]FIG. 16 is a sectional view of a gas generator of the eighthembodiment according to the present invention.

[0053]FIG. 17 is a diagram taken along arrowed line J-J of FIG. 16.

[0054]FIG. 18 is a sectional view of a gas generator of the ninthembodiment according to the present invention.

[0055]FIG. 19 is a diagram taken along arrowed line K-K of FIG. 18.

[0056]FIG. 20 is a sectional view of a gas generator of the tenthembodiment according to the present invention.

[0057]FIG. 21 is a diagram taken along arrowed line L-L of FIG. 20.

[0058]FIG. 22 is a sectional view of a gas generator of the eleventhembodiment according to the present invention.

[0059]FIG. 23 is a sectional view of a gas generator of the twelfthembodiment according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0060] Description will be given on the gas generator of the presentinvention.

[0061] The gas generator of the present invention is designed forexpanding and inflating a driver's seat airbag. In the gas generator ofthe present invention, flames of the Ignitor device are propagated inthe circumferential direction and radial direction of the housingthrough enhancer devices so that combustion of the gas generants maybroaden in the whole instantaneously, whereby the generated gas isuniformly discharged into the airbag.

[0062] In the following, certain embodiments of the gas generator of thepresent invention will be described, which are classified into twotypes. In one type, the gas generants are ignited by a plurality ofignitor devices (Cf. FIGS. 1-17). In other type, the gas generants areignited by a single ignitor device (Cf. FIGS. 18-23).

[0063] The gas generator D1 shown in FIGS. 1 and 2 is designed so as tocontrol an expansion and inflation of the airbag. The gas generator D1comprises a short cylindrical housing 1, a filter supporting member 2mounted in the housing 1, a ring partition member 5 for partitioning aninner space of the housing 1 into two combustion chambers 3, 4, filters6 mounted in the combustion chambers 3, 4, gas generants 7 packed in theeach combustion chamber 3, 4, ignitor devices 8, 9 for spouting flameinto the combustion chambers 3, 4 respectively and independently,enhancer devices 10, 11 for enhancing the flames of the ignitor devices8, 9 respectively and independently.

[0064] The housing 1 has a double cylinder structure formed by an uppercasing 12 and a lower casing 13. The housing 1 is structured so that theupper casing 12 and the lower casing 13 may be joined to each other bybutt welding (e.g. friction welding), whereby upper ends and lower endsof an outer cylinder 14 and an inner cylinder 15 can be closed by twocover plates 16, 17. The interior of the housing 1 is partitioned into aclosed space S (annular space) formed between the outer cylinder 14 andthe inner cylinder 15 and a storage space SI formed in the inside of theinner cylinder 15.

[0065] The outer cylinder 14 of the housing 1 has a plurality of gasdischarge holes 14 a so as to communicate between the closed space S andthe interior of the airbag. The gas discharge holes 14 a open in theouter cylinder 14 on the upper cover plate 16 side and are arrangedalong a circumferential direction of the housing 1 apart from each otherby a predetermined space. The gas discharge holes 14 a are closed by (a)burst plate(s) 18 stuck on an internal circumferential surface of theouter cylinder 14. The burst plate 18 is, for example, formed from ametal foil such as aluminum and serves as moisture-proof and innerpressure adjustment of the housing 1. The inner cylinder 15 has aplurality of flame leading holes 15 a communicating between the spaces Sand S1. The flame leading holes 15 a open in the inner cylinder 15 onthe upper cover plate 16 side and are arranged along the circumferentialdirection of the housing 1 apart from each other by a predeterminedspace.

[0066] A short inner cylinder 19 is integrally formed on the lower coverplate 17 of the housing 1 so as to project into the closed space S. Theshort inner cylinder 19 is disposed between the outer cylinder 14 andthe inner cylinder 15, also, which is eccentrically disposed in a radialand outward direction with respect to the axis “a” of the housing 1. Thelower cover plate 17 has a flanged cylinder 20 extending from anexternal circumferential edge of the lower cover plate 17 toward theupper cover plate 16 along a side surface of the outer cylinder 14 onthe outer diameter side. A retainer or equivalent of the airbag modulecomprising the airbag and a bag cover is attached to a flange 21 of theflanged cylinder 20.

[0067] The cylindrical filter supporting member 2 is disposed in theclosed space S of the housing 1. The filter supporting member 2 isproduced, for example, by forming a metal such as a perforated metalplate (punching metal plate) or an expanded metal plate into acylindrical form. The filter supporting member 2 is disposed in a spacebetween the outer cylinder 14 and the short Inner cylinder 19 andextends from the lower cover plate 17 to a vicinity of the upper coverplate 16. An upper end of the filter supporting member 2 is closed by aring cover plate 22 fitted around on external circumferential surface ofthe inner cylinder 15. The filter supporting member 2, the lower coverplate 17 and the ring cover plate 22 serve to partition the closed spaceS into a gas passage space S2 (annular space) on the outer cylinder 14side and a combustion space S3 (annular space) on the inner cylinder 15side. Also, the filter supporting member 2 has a plurality of gaspassage holes 2 a so as to communicate between the gas passage space S2and the combustion space S3.

[0068] The partition member 5 is fitted between an internalcircumferential surface of the filter supporting member 2 and anexternal circumferential surface of the inner cylinder 15 in substantialparallel with the cover plates 16, 17, whereby the combustion chamber S3is partitioned into the two, i.e. upper and lower combustion chambers 3,4 in a specified volume proportion. A position of the partition member 5is set by confronting an upper end of the short inner cylinder 19.

[0069] The filters 6 are disposed in the combustion chambers 3, 4,respectively. The filters 6 can be produced at a low price, for example,by forming an aggregation of a stockinet wire netting or crimped metalwire materials into a cylindrical shape. The filters 6 are disposed inthe space between the filter supporting member 2 and the short innercylinder 19. One of the filters 6 extends from the ring partition plate5 to the ring cover plate 22 in the combustion chamber 3, and the otherof the filters 6 extends from the lower cover plate 17 to the ringpartition plate 5 in the combustion chamber 4.

[0070] The gas generants 7 are packed in the combustion chambers 3, 4 onan internal circumferential side of the filters, which generate hightemperature gas by combustion. The packed amount of the gas generants 7is adjusted in advance so that the expansion and inflation of the airbagcan be controlled.

[0071] The ignitor devices 8, 9 are respectively disposed in the innercylinder 15 and the short inner cylinder 19. The ignitor device 8comprises an ignitor 23 and enhancer agents 24. The ignitor 23 is suchan electric type ignitor as ignites when an electric current flows inaccordance with a collision signals from a collision detecting sensor.The ignitor 23 is mounted on the lower cover plate 17 so as to projectinto the storage space S1 of the inner cylinder 15. The ignitor 23 isfixed thereto by crimping lugs 25 projecting from the lower cover plate17 into the storage space S1 of the inner cylinder 15. The enhanceragents 24 are loaded in the inner cylinder 15 on the upper cover plate16 side and apart from the ignitor 23 with a gap. This arrangement ofthe ignitor device 8 allows the enhancer agents 24 to be ignited by theignition of the ignitor 23 and in turn allows the flames of the enhanceragents 24 to be spouted into the combustion chamber 3 through the flameleading holes 15 a so as to ignite and burn the gas generants 7 packedin the combustion chamber 3.

[0072] The ignitor device 9 is constituted by the ignitor 26 only. Theignitor 26 is such an electric type ignitor as ignites when an electriccurrent flows in accordance with a collision signals from a collisiondetecting sensor. The ignitor 26 is disposed in the short inner cylinder19 so as to project into the combustion chamber 4. And the ignitor 26 isfixed thereto by crimping lugs 27 projecting from the short innercylinder 19 Into the combustion chamber 4. The ignitor 26 iseccentrically arranged in radial and outward direction with respect tothe axis “a” of the housing 1. And the ignitor 26 spouts the flamestoward the partition plate 5 and a surrounding space around the axis “a”of the housing 1 so as to ignite and burn the gas generants 7 packed inthe combustion chamber 4.

[0073] The enhancer devices 10, 11 comprise the enhancer agents formedinto ring-shaped plates. It is preferable that explosive compositionsbased on nitrogen-containing organic compounds as fuel with theauto-ignition function are employed as the enhancer agents. An explosivecomposition, which comprises a following mixture and binders added tothe mixture, is optimum as the explosive composition based onnitrogen-containing organic compounds as fuel with the auto-ignitionfunction. The above mixture comprises organic tetrazole compounds,oxidizing agents using nitrate as the main component, combustionmodifier including a simple metal substance such as Zr, Hf, Mo, W, Mn,Ni and Fe, or oxides thereof or sulfides thereof. Since those enhanceragents can be ignited by the ignitor devices 8, 9, the flames can beinstantaneously propagated in the circumferential direction and theradial direction of the housing. In addition to this, since the enhanceragents ignite automatically under high temperature, for example, notless than 200° C., when the gas generator Is exposed to flames in avehicle fire and the like, the enhancer agents ignite before strength ofthe gas generator deteriorates under high temperature. Consequently, theignition and burning of the gas generants 7 cause so as to prevent thehousing of the gas generator from being destroyed or damaged. Theenhancer devices 10, 11 are loaded in the combustion chambers 3, 4,respectively.

[0074] The enhancer device 10 is fitted along the internalcircumferential surface of the filter 6 and placed between the ringcover plate 22 and the gas generants 7 in substantial parallel with thering cover plate 22. The enhancer device 10 covers all over thecircumferential direction as well as the radial direction of the housing1 in direct contact with the gas generants 7 packed in the combustionchamber 3. The flames spouted out from the flame leading holes 15 a bythe ignitor device 8 are propagated around the axis “a” of the housing 1and from the inner cylinder 15 toward the outer cylinder 14. Theenhancer device 11 is disposed between the internal circumferentialsurface of the filter 6 and the external circumferential surface of theinner cylinder 15 and arranged between the ring partition plate 5 andthe ignitor 26 in substantial parallel with the ring partition plate 5.The enhancer device 11 covers all over the circumferential direction aswell as the radial direction of the housing 1 in contact with an upperend of the ignitor 26 disposed eccentrically and also in direct contactwith the gas generants 7 packed in the combustion chamber 4. As a resultof this, the flames spouted out from the ignitor 26 are propagatedaround the axis “a” of the housing 1 and toward the outer cylinder 14.

[0075] Now, operation of the gas generator D1 will be described.

[0076] When a vehicle collision is detected by the collision sensor, anelectric current flows through the ignitor 23 and the ignitor 23 ignitesthen the enhancer agents 24 fire. The flames of the enhancer agents 24are spouted from the flame leading holes 15 a into the combustionchamber 3 so as to Ignite and burn the gas generants 7 and the enhanceragents of the enhancer device 10 simultaneously. As a result of this,the flames of the ignitor 23 are transferred to the enhancer agents ofthe enhancer device 10 and are propagated in the circumferentialdirection and the radial direction of the housing 1. This causes aburning of the gas generants 7 in the combustion chamber 3 and ageneration of high temperature gas therein. The combustion in thecombustion chamber 3 broadens Instantaneously all over the whole gasgenerants 7 by the flames spouted into the combustion chamber 3 and theflames propagated by the enhancer device 10.

[0077] The high temperature gas generated in the combustion chamber 3flows Into the filter 6 for slag collection and cooling. Then the gasflows into the gas passage space S2 through the gas passage holes 2 afor uniformity. Further, the combustion in the combustion chamber 3proceeds. And, when the pressure in the housing 1 reaches apredetermined pressure, the burst plate 18 is broken. And clean gas,which is uniformed in the gas passage space S2, is discharged from thegas discharge holes 14 a into the airbag.

[0078] As a result of this, the airbag starts expanding and inflatingmoderately by a small amount of gas generated in the only combustionchamber 3.

[0079] Sequentially, an electric current flows through the ignitor 26with minute time delay after the combustion starts in the combustionchamber 3. The flames of the ignitor 26 are spouted around the shortinner cylinder 19 so as to ignite and burn the gas generants 7 in thecombustion chamber 4 and simultaneously spouted toward the enhancerdevice 11 so as to ignite the enhancer agents of the enhancer device 11.As a result of this, the flames of the ignitor 26 are transferred to theenhancer agents of the enhancer device 11 and propagated in thecircumferential direction and the radial direction of the housing 1.Consequently, the gas generants 7 in the combustion chamber 4 burn andhigh temperature gas generates therein.

[0080] The combustion in the combustion chamber 4 are instantaneouslyspread in the circumferential direction and the radial direction of thehousing 1 by the flames spouted from the ignitor 26 directly into thecombustion chamber 4 and the flames propagated by the enhancer device11. Then, the combustion in the combustion chamber 4 broadens all overthe whole of gas generants 7 instantaneously.

[0081] As a result of this, there is no partial combustion which occursin the vicinity of the ignitor 26 eccentrically disposed in thecombustion chamber 4. The gas can be uniformly generated inside thehousing 1.

[0082] The high temperature gas generated in the combustion chamber 4flows into the filter 6 for slag collection and cooling thereat. Then,the gas flows into the gas passage space S2 for uniformity and isdischarged from the gas discharging holes 14 a into the airbaguniformly. Consequently, the airbag is expanded and inflated rapidly bya large amount of clean gas discharged from the both combustion chambers3, 4.

[0083] As a result of this, in the initial stage of inflation, theairbag starts expanding and inflating moderately by a small amount ofgas generated in the only one combustion chamber 3, after minute timepasses, the airbag is expanded and inflated rapidly by a large amount ofgas generated in the both combustion chambers 3, 4.

[0084] In addition, the whole airbag is smoothly expanded and inflatedby the gas uniformly discharged from the gas discharging holes 14 awithout any partial expansion and inflation.

[0085] When the ignitors 23, 26 of the ignitor devices 8, 9 ignite bythe electric current, minute time delay between the ignitions of theignitors 23, 26 is not always necessary. It is chosen appropriately soas to meet the collision patterns of the vehicle

[0086] For example, in the case of a high critical collision such as afrontal clash or a head-on clash with high speed, the ignitors 23, 26are concurrently ignited by the electric current so that the airbag canbe expanded and inflated rapidly by a large amount of gases generated inthe both combustion chambers 3, 4. In the case of a medium criticalcollision, the ignitors 23, 26 are ignited by the electric current withminute time delay between the ignitions of the ignitors 23, 26 so thatthe airbag can be moderately expanded and inflated by a small amount ofgas in the initial stage, after the minute time passes, the airbag canbe rapidly expanded and inflated by a large amount of gases. Further, inthe case of a light critical collision, for example, only one ignitor 23ignites by an electric current so that the airbag can be moderatelyexpanded and inflated by a small amount of gas with taking acomparatively long time.

[0087] Thus, according to the gas generator D1, the amount of gasdischarged into the airbag can be adjusted by selecting the ignitions ofthe ignitor devices 8, 9 In response to the collision patterns ofvehicle, whereby, the expansion and inflation of the airbag can becontrolled.

[0088] By the enhancer devices 10, 11 for propagating the flames of theignitor devices 8, 9 in the circumferential direction and the radialdirection of the housing 1, the combustion of the gas generants 7 in thecombustion chambers 3, 4 can broaden to the whole instantaneously.Accordingly, the amount of gas discharged from the gas discharging holes14 a into the airbag can be uniformed.

[0089] Consequently, even when the ignitor device 9 is eccentricallydisposed in the radial and outward direction with respect to the axis“a” of the housing 1, the whole airbag can be smoothly expanded andinflated without any partial expansion and inflation. Next, referencewill be made to the gas generator D2 shown in FIGS. 3 and 4.

[0090] The gas generator D2 shown in FIGS. 3 and 4 has a differentstructure from the gas generator D1. In the gas generator D2, theenhancer device 11 and the ring partition plate 5 are integrally formed.In FIGS. 3 and 4, the same reference characters as those of FIGS. 1 and2 show the same elements as those of FIGS. 1 and 2. Therefore,explanations about them are omitted.

[0091] In the gas generator D2 of FIGS. 3 and 4, the enhancer agents ofthe enhancer device 11 are loaded in the interior of the ring partitionmember 5 so as to be integrally combined therewith. An annular enhancinggroove 28 is formed in the ring partition member 5, in which theenhancer agents are charged.

[0092] The enhancing groove 28 is formed so as to confront the top endof the ignitor 26 of the ignitor device 9 and extend along the externalcircumferential surface of the inner cylinder 15 surrounding the axis“a” of the housing 1. The enhancing groove 28 is formed so as to opentoward the combustion chamber 4 with a predetermined width “t” andprojects into the combustion chamber 3 with a predetermined depth. Theenhancer agents of the enhancer device 11 are stored in the interior ofthe enhancing groove 28 of the ring partition member 5, whereby, theenhancing groove 28 spreads in the circumferential direction and radialdirection of the housing 1. The enhancing groove 28 storing the enhancerdevice 11 is tightly sealed by a metal plate 29 stuck on the ringpartition plate 5. The metal plate 29 is formed from a metal foil suchas an aluminum foil, and formed into a ring-shaped form. The metal plate29 closes the enhancing groove 28 at the inside of the combustionchamber 4. The metal plate 29 is burst by the flames spouted out fromthe ignitor 26 so that the enhancer agents of the enhancer device 11 canbe ignited by the flames. The enhancer agents of the enhancer device 11are indirectly contacted with the gas generants 7 through the metalplate 29.

[0093] Now, operation of the gas generator D2 will be described.

[0094] When the ignitor 23 is ignited by an electric current inaccordance with a detection of a vehicle collision, the combustion inthe combustion chamber 3 broadens to the whole of the gas generantsinstantaneously by the flames spouted into the combustion chamber 3 andthe flames propagated by the enhancer device 10 as well as the case ofFIGS. 1,2. The high temperature gas generated in the combustion chamber3 undergoes a slag collection and cooling process during passing throughthe filter 6. Then, the gas is made uniform in the gas passage space S2.And thereafter the uniform gas is discharged into the airbag.Consequently, the airbag starts expanding and inflating moderately by asmall amount of clean gas generated in the only one combustion chamber3.

[0095] Sequentially, the ignitor 26 is ignited by an electric currentafter minute time passes from the start of combustion in the combustionchamber 3. Then, the flames of the ignitor 26 are spouted around theshort inner cylinder 19 so as to burn the gas generants 7 in thecombustion chamber 4 and are simultaneously spouted toward the ringpartition plate S so as to burst the metal plate 29. And, the enhanceragents of the enhancer device 11 are ignited. As a result of this, theflames of the ignitor 26 are transferred to the enhancer agents of theenhancer device 11 and are propagated in the circumferential directionand the radial direction of the housing 1. Then, the gas generants 7 inthe combustion chamber 4 burn and high temperature gas generatestherein. At this time, the flames transferred to the enhancer agents ofthe enhancer device 11 runs around the external circumferential surfaceof the inner cylinder 15 because of the configuration of the enhancinggroove 28 so as to propagate the flames from the top end of the ignitor26 to the opposite space side between the inner cylinder 15 and thefilter 6. The thickness of the metal plate 29 is set so that the metalplate 29 may be burst by the burning of the enhancer agents.

[0096] Accordingly, the combustion in the combustion chamber 4 areinstantaneously spread in the circumferential direction and the radialdirection of the housing 1 by the flames spouted from the ignitor 26directly into the combustion chamber 4 and the flames propagated throughthe enhancer device 11 and the enhancing groove 28 of the ring partitionplate 5. Then, the combustion broadens all over the whole of gasgenerants 7.

[0097] As a result, in the combustion chamber 4, there is no partialcombustion in the vicinity of the ignitor 26 eccentrically disposed. Thegas can be uniformly generated over the whole of the housing 1. The hightemperature gas generated in the combustion chamber 4 flows into thefilter 6. Thereat, the high temperature gas undergoes the slagcollection and cooling process. After the high temperature gas becomesuniform in the gas passage space S2, it is discharged into the airbag.Thus, the airbag is rapidly expanded and inflated by a large amount ofclean gas discharged from the both combustion chambers 3, 4.

[0098] In case of the gas generator D2 as well as the case of the gasgenerator D1, the expansion and inflation of the airbag can becontrolled by choosing a minute time delay between the ignitions of theignitors 23, 26 appropriately in response to the collision patterns ofvehicle.

[0099] Thus, according to the gas generator D2 as well as the gasgenerator D1, the expansion and inflation of the airbag can becontrolled and also the whole airbag can be smoothly expanded andinflated without any partial expansion and inflation.

[0100] Next, reference will be made to the gas generator D3 shown inFIGS. 5 to 7.

[0101] In the gas generator D3 of FIGS. 5 to 7, the enhancer device 11has an enhancing groove 28 and a cushioning member 30. In FIGS. 5 to 7,the same reference characters as those of FIGS. 3 and 4 show the sameelements as those of FIGS. 3 and 4. Therefore, explanations about themare omitted.

[0102] In the gas generator D3 of FIGS. 5 to 7, an enhancing space S6 ofthe enhancer device 11 may be formed by the cushioning member 30 and theenhancing groove 28 without enhancer agent. The cushioning member 30 isfitted between the ring partition member 5 in the combustion chamber 4and the gas generants 7. The cushioning member 30 abuts on the ringpartition member 5 so as to shut the interior of the enhancing groove 28from the combustion chamber 4 The cushioning member 30 constructs theannular enhancing space S6 with the interior of the enhancing groove 28.The annular enhancing space S6 extends along an external circumferentialsurface of the inner cylinder 15 surrounding the axis “a” of the housing1 in accordance with the configuration of the enhancing groove 28. A topend portion of the ignitor 26 is fitted in the cushioning member 30 thenexposes to the enhancing space S6. The cushioning member 30 has aplurality of enhancing holes 30 a so that the enhancing space S6 mayopen into the combustion chamber 4. The enhancing holes 30 a arearranged along the annular enhancing space S6 and communicate betweenthe enhancing space S6 and the combustion chamber 4. A diameter of eachenhancing hole 30 a is set so that the gas generants 7 may not enter theenhancing space S6 therethrough.

[0103] The cushioning member 30 has functions of preventing the gasgenerants 7 from being powdered by vibration and preventing the gasgenerants 7 from entering the interior of the enhancing space S6. Also,the cushioning member 30 serves as heat insulating material so as tosuppress heat transfer between the combustion chambers 3, 4.Accordingly, materials such as ceramic sheets having the heat insulatingproperty (e.g. ceramic fiber sheets and the like)or elastic materials(e.g. silicone foam materials and the like) are preferably used as thecushioning member 30.

[0104] Now, operation of the gas generator D3 will be described.

[0105] When vehicle collision is detected by the collision sensor andthen the ignitor 23 is ignited by an electric current, the combustion inthe combustion chamber 3 broadens all over the whole of the gasgenerants 7 instantaneously by the flames spouted into the combustionchamber 3 and the flames propagated by the enhancer device 10 in thesame manner as in FIGS. 1 and 2. The high temperature gas generated inthe combustion chamber 3 undergoes slag collection and cooling processin the filter 6. Then, the gas is uniformed in the gas passage space S2.Thereafter the gas is discharged into the airbag. As a result of this,the airbag starts expanding and inflating moderately by a small amountof clean gas generated in the only one combustion chamber 3.

[0106] Sequentially, the ignitor 26 is ignited by the electric currentwith minute time delay after the start of combustion in the combustionchamber 3. The flames are spouted from the ignitor 26 into the annularenhancing space S6, then, propagated along the enhancing space S6 in thecircumferential direction and the radial direction of the housing 1, andthen, sequentially spouted into the combustion chamber 4 from theenhancing holes 30 a of the cushioning member 30. The flames cause thecombustion of the gas generants 7 in the combustion chamber 4 and a hightemperature gas is generated therein. At this time, the flames spoutedinto the enhancing space S6 run around the external circumferential faceof the inner cylinder 15 so as to be propagated from the top end of theignitor 26 to the opposite space side between the inner cylinder 15 andthe filter 6 because of the configuration of the enhancing space S6.

[0107] Thus, the combustion in the combustion chamber 4 is propagatedthrough the enhancing space S6 from the ignitor 26 and instantaneouslyspreads in the circumferential direction and the radial direction of thehousing 1 by the flames spouted out from the enhancing holes 30 a of thecushioning member 30. Consequently, the combustion in the combustionchamber 4 broadens all over the whole of gas generants 7.

[0108] Therefore, in the combustion chamber 4, there is no partialcombustion In vicinity of the ignitor device 26 disposed on theeccentric position. The gas can be uniformly generated all over thewhole area in the housing 1.

[0109] The high temperature gas generated in the combustion chamber 4flows into the filter 6 for slag collecting and cooling. After unifyingin the gas passage space S2, the gas is discharged into an airbag. And,the airbag is rapidly expanded and inflated by a large amount of cleangas discharged from the both combustion chambers 3, 4.

[0110] In case of the gas generator D3 as well as the case of the gasgenerator D1, the expansion and inflation of the airbag can becontrolled by choosing a minute time delay between the ignitions of theignitors 23, 26 appropriately in response to the collision patterns ofvehicle.

[0111] Thus, according to the gas generator D3 as well as the gasgenerator D1, the expansion and inflation of the airbag can becontrolled and also the whole airbag can be smoothly expanded andinflated without any partial expansion and inflation.

[0112] In addition, since the gas generator D3 is structured so that theenhancing groove 28 projecting into the combustion chamber 3 may beformed in the ring partition plate 5 and also the top end portion of theignitor 26 may be fitted into the enhancing space S6 of the enhancinggroove 28, the housing 1 can be reduced in axial length and a small-sizegas generator D3 can be provide.

[0113] According to the gas generators D1-D3, the enhancer devices 10,11 are mounted in the combustion chambers 3, 4 respectively. However,another structure can be applied as shown in FIG. 8. In FIG. 8, theenhancer device 11 is mounted in only the combustion chamber 4 in whichthe ignitor 9 is disposed on the eccentric position.

[0114] According to the gas generator D4 of FIG. 8, the expansion andinflation of the airbag can be controlled in response to the collisionpatterns of vehicle as well as the gas generator D1. In combustionchamber 4, the flames from the ignitor 26 can be propagated in thecircumferential direction and the radial directions of the housing 1 bythe enhancer device 11 as well as the gas generator D1-D3. Thereby, thecombustion broadens all over the whole of gas generants instantaneously.Therefore, the whole airbag can be smoothly expanded and inflatedwithout any partial expansion and inflation.

[0115] Next, reference will be made to the gas generator D5 shown inFIGS. 9 and 10.

[0116] The gas generator D5 shown in FIGS. 9 and 10 is different fromthe gas generator D1 in the following point. A housing 31 has a singlecylinder structure and each ignitor device 38, 39 is disposed on aneccentric position with respect to an axis “a” of the housing 31.

[0117] The gas generator D5 shown in FIGS. 9 and 10 comprises the shortcylindrical housing 31, a ring partition member 35 for partitioning theinterior of the housing 31 into two combustion chambers 33, 34,respective filters 36 mounted in the housing 31, gas generants 37 packedin the respective combustion chambers 33, 34, ignitor devices 38, 39 forspouting flames into the combustion chambers 33, 34 respectively andenhancer devices 40, 41 for propagating the flames of the ignitordevices 38, 39 respectively.

[0118] The housing 31 has a single cylinder structure formed by an uppercasing 42 and a lower casing 43. As concerns the housing 31, the upperand lower casings 42 and 43 are joined to each other by butt welding(e.g. friction welding), whereby, an upper end and a lower end of anouter cylinder 44 are respectively closed by two cover plates 46, 47.Accordingly, a closed space S is formed in the interior of the housing31.

[0119] The outer cylinder 44 of the housing 31 has a plurality of gasdischarge holes 44 a so as to communicate between the closed space S andthe interior of the airbag. The gas discharge holes 44 a open in theouter cylinder 44 on the upper cover plate 46 side and are arrangedapart from each other by a predetermined space along a circumferentialdirection of the housing 31. The gas discharge holes 44 a are closed by(a) burst plate(s) 48 stuck on the internal circumferential surface ofthe outer cylinder 44. For example, the burst plate 48 is formed from ametal foil such as aluminum. And the burst plate 48 serves asmoisture-proof and inner pressure adjustment of the housing 31.

[0120] Two long and short Inner cylinders 45, 49 are integrally formedon the lower cover plate 47 of the housing 31 so as to project into theclosed space S. The respective inner cylinders 45, 49 is eccentricallydisposed in a radial and outward direction so as to be asymmetrical withrespect to the axis “a” of the housing 31. As an example of anotherarrangements, the respective inner cylinders 45, 49 may be pointsymmetrically disposed with respect to the axis “a” of the housing 31. Aflanged cylinder 50 is formed on an external circumferential edge of thelower cover plate 47 so as to extend toward the upper cover plate 46along a side surface of the outer cylinder 44 on the outer diameterside. A retainer or equivalent of the airbag module comprising theairbag and a bag cover is attached to a flange 51 of the flangedcylinder 50.

[0121] The partition member 35 is fitted around the externalcircumferential surface of the long inner cylinder 45 in substantialparallel with the cover plates 46, 47. The partition member 35 togetherwith the outer cylinder 44 and the cover plates 46, 47 partitions theclosed space into the two upper and lower partitioned spaces S4, S5 in aspecified volume proportion.

[0122] The partitioned spaces S4, S5 communicate with each other throughthe space between an external circumferential surface of the ringpartition plate 35 and the internal circumference surface of the outercylinder 44.

[0123] The filters 36 are mounted in the partitioned spaces S4, S5respectively. The filter 36 can be formed, for example, by forming anaggregation of a stockinet wire netting, a plain-woven wire netting orcrimped metal wire materials into a cylindrical shape. Thereby thefilter 36 can be produced at a low price. The each filter 36 is disposedin the space between the outer cylinder 44 and the short inner cylinder49. In the partitioned space S4, one of filters 36 extends from the ringpartition plate 35 to a vicinity of the upper cover plate 46. In thepartitioned space S5, other of filters 36 extends from the lower coverplate 47 to the ring partition plate 35. The filter 36 set in thepartitioned space S4 is closed at a top end thereof by another coverplate 52. The filter 6 and the ring partition plate 35 together with thecover plate 52 partition the partitioned spaces S4, S5 into the gaspassage space S2 (annular space) on the outer cylinder 44 side and thecombustion chambers 33, 34 on the inner cylinder 45, 49 side.

[0124] The gas generants 37, which generate high temperature gas bycombustion, are packed in the combustion chambers 33, 34 respectively.The packing amount of the gas generants 37 is adjusted in advance sothat the expansion and inflation of the airbag can be controlled.

[0125] The ignitor devices 38, 39 are mounted in the inner cylinders 45,49 respectively. The ignitor devices 38, 39 consist of only ignitors 53,54 respectively, The each ignitor 53, 54 is the electric type whichignites by an electric current in accordance with collision signals froma collision detecting sensor. The each ignitor 53, 54 is disposed in theinner cylinder 45, 49 so as to project into the combustion chamber 33,34, then fixed thereto by crimping lugs 55 projecting from the innercylinder 45, 49 into the combustion chamber 33, 34. The each ignitordevice 38, 39 is disposed on the radially outwardly eccentric positionwith respect to the axis “a” of the housing 31. The each ignitor device38, 39 spouts the flames toward the cover plate 52 or the ring partitionplate 35 and a space around the external circumferential surface of thelong or short inner cylinder 45,49. Thereby, the gas generants 37 packedin the each combustion chamber 33, 34 are ignited and burned.

[0126] The enhancer device 40, 41 are mounted in the combustion chambers33, 34 respectively. The enhancer device 40 consists of a circular platemade of enhancer agents and is fitted in along the internalcircumferential surface of filter 36. The enhancer device 40 is arrangedbetween the ignitor device 38 and the cover plate 52 in substantiallyparallel with the cover plate 52. The enhancer device 40 confronts a topsurface of the ignitor 53 disposed on the eccentric position and extendsin the circumferential direction and the radial direction of the housing31 in directly contact with the gas generants 37 packed in thecombustion chamber 33. The enhancer device 40 propagates the flamesspouted out from the ignitor 53 around the axis “a” of the housing 31and toward the outer cylinder 44.

[0127] The enhancer device 41 consists of a ring-shaped plate made ofthe enhancer agents and is fitted between the internal circumferencesurface of the filter 36 and the outer circumferential surface of thelong inner cylinder 45. The enhancer device 41 is placed between thering partition plate 35 and the ignitor device 39 in substantiallyparallel with the ring partition plate 35. The enhancer device 41contacts with the top end of the ignitor 54 disposed eccentrically anddirectly with the gas generants 37 packed in the combustion chamber 34.And the enhancer device 41 extends in the circumferential direction andthe radial direction and propagates the flames spouted out from theignitor 54 around the axis “a” of the housing 31 and toward the outercylinder 44. As well as the case of the gas generator D1, an explosivecomposition which includes nitrogen-containing organic compounds as fueland has auto-ignition function, is preferably used as the enhanceragents of the each enhancer device.

[0128] The operation of this gas generator D5 will be easily understoodfrom what have been described on the gas generators D1-D4.

[0129] Since the gas generator D5 is structured so that the housing 31may have a single cylinder structure, the structure of the gas generatorD5 is simplified as compared with the double cylinder structure adoptedin the gas generators D1-D4. Therefore, manufacturing costs can bereduced. Preferably, the housing 31 comprises the casings 42, 43 made ofstainless steel plates by means of press-molding. The housing 31 formedfrom stainless steel is superior in heat resistance and pressureresistance to the housing formed from aluminum alloy and the like. Whenthe housing 31 having excellent heat resistance and pressure resistanceis used, the non-azide gas generants that are being increasingly used inrecent years can be used as a substitute for the azide gas generantsthat have been used so far. Since the non-azide gas generants have theproperty of easily producing high temperature and high pressure gas ascompared with the azide gas generants, the housing 31 is required tohave high heat resistance and pressure resistance. This requirement canbe supplied easily by use of the housing 31 having the single cylinderstructure formed from stainless steel plates or equivalent.

[0130] Next, reference will be made to the gas generator D6 shown inFIGS. 11 and 12.

[0131] The gas generator D6 shown in FIGS. 11 and 12 is different fromthe gas generator D5 in the following point. In the gas generator D6,the enhancer device 41 and the ring partition plate 35 are integrallyformed. The same reference characters as those of FIGS. 9 and 10 showthe same elements as those of FIGS. 9 and 10. Therefore, explanationsabout them are omitted.

[0132] In the gas generator D6 of FIGS. 11 and 12, the enhancer agentsof the enhancer device 41 are loaded In the interior of the ringpartition member 35 so as to be integrated with the ring partitionmember 35 already described in the FIGS. 3 and 4. An annular enhancinggroove 58 is formed in the ring partition member 35 so as to be chargedwith the enhancer agents therein and sealed tight by the metal plate 29.The enhancing groove 58 confronts the top end of the ignitor 54 of theignitor device 39 and extends along the outer circumferential surface ofthe long inner cylinder 45 placed on a periphery of the axis “a” of thehousing 1. Structures of remaining parts are the same structures asdescribed in FIGS. 9 and 10.

[0133] The operation of this gas generator D6 will be fully understoodfrom what have been described on the gas generators D1-D4.

[0134] The gas generator D7 shown in FIGS. 13-15 Is different from thegas generator D6 in the following point. In the gas generator D7, theenhancer device 40 and the cover plate 52 are integrally formed.Structures of remaining parts are the same structures as described inFIGS. 11 and 12. The same reference characters as those of FIGS. 11 and12 show the same elements as those of FIGS. 11 and 12.

[0135] The operation of this gas generator D7 will be fully understoodfrom what have been described on the gas generators D5 and D6.

[0136] Further, the gas generator D8 shown in FIGS. 16, 17 is differentfrom the gas generator D7 in the following point. In the gas generatorD8, the enhancer device 41 comprises the enhancing groove 58 and acushioning member 60. In FIGS. 16,17, the same reference characters asthose of FIGS. 13 and 15 show the same elements as those of FIGS. 13 and15. Therefore, explanations about them are omitted.

[0137] As already described in the FIGS. 5-7, the annular enhancingspace S6 constructing the enhancer device 41 is formed by the cushioningmember 60 and the enhancing groove 58 without charged enhancer agents.The cushioning member 60 is fitted between the ring partition member 35and the gas generants 37 in the combustion chamber 34. The cushioningmember 60 abuts the ring partition member 35 so as to shut out theinterior space of the enhancing groove 58 from the combustion chamber 34side. The annular enhancing space S6 is defined by the cushioning member60 and an inside surface of the enhancing groove 58. The enhancing spaceS6 extends along the external circumferential surface of the long innercylinder 45 placed in the periphery of the axis “a” of the housing 1 inaccordance with the configuration of the enhancing groove 58. The topend portion of the ignitor 54 is fitted in the cushioning member 60 soas to be exposed in the enhancing space S6. The cushioning member 60 hasa plurality of enhancing holes 60 a so that the enhancing space S6 mayopen toward the combustion chamber 34. The enhancing holes 60 a arearranged along the annular enhancing space S6 and communicate betweenthe enhancing space S6 and the combustion chamber 34. A diameter of theeach enhancing hole 60 a is set so that the gas generants 37 may notenter the enhancing space S6 therethrough. As already described in thegas generator D3, it is preferable that materials such as ceramic sheetshaving the heat insulating property (e.g. ceramic fiber sheets and thelike) or elastic materials (e.g. silicone foam materials and the like)are used as the cushioning member 30.

[0138] The operation of this gas generator D8 will be easily understoodfrom what have been described on the gas generators D3 and D6.

[0139] Next, reference will be made to the gas generator D9 shown inFIGS. 18 and 19.

[0140] The gas generator D9 shown in FIGS. 18 and 19 is different fromthe gas generators D1-D8 in the following point. In the gas generatorD9, only one ignitor device 78 is used to burn the gas generants 77 andthe ignitor device 78 is eccentrically disposed with respect to the axis“a” of the housing 71.

[0141] The gas generator D9 shown in FIGS. 18 and 19 comprises a shortcylindrical housing 71, a filter 76 mounted in the housing 71, gasgenerants 77 packed in the housing 71, an ignitor device 78 for spoutingflames into the housing 71 and an enhancer device 80 for propagating theflames of the ignitor device 78.

[0142] The housing 71 has a single cylinder structure formed by an uppercasing 82 and a lower casing 83. In the housing 71, the casings 82 and83 are joined to each other by butt welding (e.g. friction welding),whereby, upper and lower ends of an outer cylinder 84 can berespectively closed by two cover plates B6, 87. Accordingly, the closedspace S is formed in the interior of the housing 71.

[0143] The outer cylinder 84 of the housing 71 has a plurality of gasdischarge holes 84 a for communicating between the closed space S andthe interior of the airbag. The gas discharge holes 84 a open on theupper cover plate 86 side of the outer cylinder 84 and are arrangedapart from each other by a predetermined space in a circumferentialdirection of the housing 71. The each gas discharge holes 84 a is closedby a burst plate 88 stuck on an internal circumferential surface of theouter cylinder 84. The burst plate 88 is formed from, for example, ametal foil such as aluminum. The burst plate 88 serves as moisture-proofand inner pressure adjustment of the housing 71.

[0144] A long inner cylinder 85 is integrally formed on the lower coverplate 87 of the housing 71 so as to project into the closed space S. Theinner cylinder 85 is eccentrically disposed in radial and outwarddirection with respect to the axis “a” of the housing 71. A flangedcylinder 90 is formed on an external circumferential edge of the lowercover plate 87 so as to extend toward the upper cover plate 86 along aside surface on the outer diameter side of the outer cylinder 84. Aretainer or equivalent of the airbag module comprising the airbag and abag cover is attached to a flange 91 of the flanged cylinder 90. Aretainer or equivalent of the airbag module comprising the airbag and abag cover is attached to a flange 91 of the flanged cylinder 90.

[0145] The filter 76 is mounted in the closed space S of the housing 71.The filter 76 can be formed, for example, by molding an aggregation of astockinet wire netting or crimped metal wire materials Into acylindrical shape, whereby the filter 76 can be produced at a low price.The filter 76 is coaxially disposed with respect to the axis “a” of thehousing 71 and extends from the lower cover plate 87 to a vicinity ofthe upper cover plate 86. A top end of the filter 76 is closed byanother cover plate 92. The filter 76 together with the lower coverplate 87 and the cover plate 92 partitions the closed spaces S into thegas passage space S2 (annular space) on the outer cylinder 84 side andthe combustion chamber 75 on the long inner cylinder 85 side. An annularenhancing groove 73 is formed in the cover plate 92 so as to store theenhancer agents. The enhancing groove 73 is formed at an eccentricposition with respect to the axis “a” of the housing 71 so as toconfront the top end of the ignitor device 78. The enhancing groove 73opens in the combustion chamber 75 at a predetermined open width “t” andprojects toward the upper cover plate 86 side at a predetermined depth.The gas generants 77, which generate high temperature gas by combustion,are packed in the combustion chamber 75.

[0146] The Ignitor device 78 is installed in the long inner cylinder 85.The ignitor device 78 consists of only an ignitor 93. The ignitor 93 isthe electric type which ignites by an electric current flowing inaccordance with collision signals from the collision detecting sensor.The ignitor 93 is mounted in the long inner cylinder 85 so as to projectinto the combustion chamber 75. The ignitor 93 is fixed by crimping lugs94 projecting from the long inner cylinder 85 into the combustionchamber 75.

[0147] The ignitor device 78 is eccentrically disposed in a radial andoutward direction with respect to the axis “a” of the housing 71. Theignitor device 78 spouts flames toward the cover plate 92 and asurrounding space around the long inner cylinder 85 then ignites andburns the gas generants 77 packed in the combustion chamber 75.

[0148] The enhancer device 80 is provided in the combustion chamber 75and comprising the enhancer agents. As well as the case of the gasgenerator D1, an explosive composition which includesnitrogen-containing organic compounds as fuel and has auto-ignitionfunction, is preferably used as the enhancer agents of the enhancerdevice. The enhancer agents of the enhancer device 80 are stored in theinterior of the enhancing groove 73 of the cover plate 92 so as toextend in circumferential direction and the radial direction of thecombustion chamber 75. The enhancing groove 73 with the enhancer agentsof the enhancer device 80 therein is tightly sealed by a metal plate 74stuck to the cover plate 92. The metal plate 74 is, for example, formedfrom a metal foil such as an aluminum foil into a ring-shaped form andcloses the enhancing groove 73 on the combustion chamber 75 side. Themetal plate 74 is burst by the flames spouted out from the ignitor 93 sothat the enhancer agents of the enhancer device 80 can be ignited by theflames. The enhancer device 80 is indirectly contact with the gasgenerants 77 through the metal plate 74 in the combustion chamber 75.

[0149] Now, operation of the gas generator D9 will be described.

[0150] When a vehicle collision is detected by a collision sensor, theignitor 93 ignites by an electric current. The flames of the ignitor 93are spouted toward a surrounding space around the long inner cylinder 85so as to burn the gas generants 77 and are simultaneously spouted towardthe cover plate 92 so as to burst the metal plate 74, after that, Ignitethe enhancer agents of the enhancer device 80. Thus, the flames of theignitor 93 are transferred to the enhancer agents of the enhancer device80 and are propagated in the circumferential direction and the radialdirection of the housing 71. And the gas generants 77 are burned thenhigh temperature gas generates. At this time, the flames transferred tothe enhancer agents of the enhancer device 80 run along theconfiguration of the enhancing groove 73 and are propagated from the topend of the ignitor 93 to a side opposite to the eccentric side. Athickness of the metal plate 74 is set so as to be burst by thecombustion of the enhancer agents.

[0151] Thus, the combustion in the combustion chamber 75 areinstantaneously spread in the circumferential direction and the radialdirection of the housing 71 by the flames spouted from the ignitor 93directly into the combustion chamber 75 and the flames propagated viathe enhancing groove 73 of the cover plate 92 and the enhancer device80. Consequently, the combustion in the combustion chamber 75 broadensall over the whole of gas generants.

[0152] Accordingly, in the combustion chamber 75, no local combustionoccurring in the vicinity of the ignitor device 78 eccentricallydisposed, And, the gas can be uniformly generated all over the whole ofthe housing 71. The airbag can be smoothly and uniformly expanded andinflated by a large amount of gas generated in the combustion chamber 75without any partial expansion and inflation.

[0153] In addition, the gas generator D9 is preferable for use of thenon-azide gas generants because of having the housing 71 of a singlecylinder structure as well as the case of the gas generator D9.

[0154] Next, the gas generator D10 of FIGS. 20 and 21 is different fromthe gas generator D9 in the following point. An annular enhancing spaceS6 constructing the enhancer device 41 is formed by the cushioningmember 70 and the enhancing groove 73 without charged enhancer agents.The same structure as the enhancer device 41 of the gas generator D3 aspreviously mentioned is applied. Structures of remaining parts are thesame structures as described in FIGS. 18 and 19. In FIGS. 20 and 21, thesame reference characters as those of FIGS. 18 and 19 show the sameelements as those of FIGS. 18 and 19. The cushioning member 70 has aplurality of enhancing holes 70 a so that the enhancing space S6 mayopen into the combustion chamber 75. The enhancing holes 70 a arearranged along the annular enhancing space S6. As already described inthe gas generator D3, materials such as ceramic sheets having the heatinsulating property (e.g. ceramic fiber sheets and the like) or elasticmaterials (e.g. silicone foam materials and the like) are used as thecushioning member 70.

[0155] The operation of the enhancer device of the gas generator D10 isthe same as the enhancer device 41 of the gas generator D3. The flamesof the ignitor 93 are propagated in the circumferential direction andthe radial direction of the housing 1 through the enhancing space S6.The combustion In the combustion chamber 75 broadens all over the wholeof the combustion chamber 75.

[0156] Next, the gas generator D11 of FIGS. 22 is different from the gasgenerator D9 in the following point. The ignitor device 78 is coaxiallymounted with respect the axis “a” of the housing 71 and also theenhancer device 80 is separated from the cover plate 92. The samestructures as the enhancer device 40 and the cover plate 52 of the eachgas generators D5, D6 previously described are applied. Structures ofremaining parts are the same structures as described in FIGS. 18 and 19.In FIG. 22, the same reference characters as those of FIGS. 18 and 19show the same elements as those of FIGS. 18 and 19.

[0157] The operation of the gas generator D11 is the same operation asthe gas generator D9.

[0158] Finally, the gas generator D12 of FIG. 23 is different from thegas generator D1 in the following point.

[0159] In the gas generator D12, only single ignitor device 8 forburning the gas generants 7 and only single combustion chamber 95 areprovided in the housing 1 without such provisions as the short innercylinder 19 and the ring partition plate 5 for partitioning thecombustion space S3 inside the filter 6. Structures of remaining partsare the same structures as described in FIG. 1. In FIG. 23, the samereference characters as those of FIG. 1 show the same elements as thoseof FIG. 1.

[0160] The operation of the gas generator D12 is as follows. Whenvehicle collision is detected by the collision sensor, the ignitor 23ignites then the enhancer agents 24 ignite. The flames of the enhanceragents 24 are spouted from the flame leading holes 15 a into thecombustion chamber 95. The spouted flames ignite and burn the gasgenerants 7 and simultaneously ignite the enhancer agents of theenhancer device 10. Thus, the flames of the ignitor 23 are transferredto the enhancer agents of the enhancer device 10 and are propagated inthe circumferential direction and the radial direction of the combustionchamber 95, whereby, the gas generants 7 burn then high temperature gasis generated. The combustion in the combustion chamber 95 broadens allover the whole of the gas generants 7 instantaneously by the flamespouted into the combustion chamber 95 and the flames propagated by theenhancer device 10.

[0161] Therefore, in the combustion chamber 95, there is no partialcombustion and the gas can be uniformly generated all over the whole inthe housing 1. The airbag can be smoothly expanded and inflated by alarge amount of gas generated in the combustion chamber 95 without anypartial expansion and inflation of the airbag.

[0162] In the gas generators D1-D12 of the present invention, theirindividual structures of the enhancer devices 10, 11, 40, 41 and 80described thereon may be mutually applied among them.

[0163] In case of the plate type enhancer device including a ring-likeplate shape and a plate-like shape, an optimum enhance property forburning the gas generants can be obtained by properly changing athickness of the plate type enhancer device. An optimum amount ofenhancer agent for burning the gas generants and an optimum enhancingspace for transferring the flames of the Ignitor can be obtained byproperly selecting the dimensions such as width and depth of theenhancing groove of the ring partition plate or cover plate in thehousing. Further, the enhance property of the enhancer device can bechanged by properly changing the components of the enhancer agent.

[0164] It is not always necessarily for the enhancer device to extendover around the entire circumference. The enhancer may be formed in anyshape to transfer the flames of the ignitor device In thecircumferential direction and radial direction. For example, theenhancer device may be formed in U-shape.

[0165] Further, the enhancing space S6 of the enhancer device may beformed by the enhancing groove only, without limiting to the combinationof the enhancing groove and the cushioning member.

[0166] While in the gas generators D1-D8 of the present invention, thecombustion chambers 3; 4, 33; 44 illustrated are structured tocommunicate therebetween through the gas passage space S2, thisstructure is not limitative. For example, the combustion chambers may beso structured as to be mutually closed up by fitting the ring partitionplate around the Inside of the outer cylinder. In the structure whereinthe combustion chambers 3; 4, 33; 44 communicate with each other, thehigh temperature gas generated in each of the combustion chambers can beled into the other combustion chamber through the gas passage space S2and the filters, to burn the gas generants packed therein.

[0167] While in the illustrated gas generators D1-D8, the two upper andlower combustion chambers are formed by a single ring partition plate,the present invention may alternatively adopt the structure thatmulti-level combustion chambers are formed by using two or more ringpartition plates. In this alternative, a multistage controlled expansionand inflation of the airbag can be provided by the ignitor device beingmounted in the multi-level combustion chambers, one in each combustionchamber.

[0168] Further, while in the illustrated gas generators D1-D8, theinterior of the housing is partitioned into a plurality of combustionchambers, the present invention may alternatively adopt the structurethat the interior of the housing is in the form of a single combustionchamber, rather than being partitioned, and a plurality of ignitordevice is used for igniting and burning the gas generants. In thisalternative, one or two or more ignitor devices are mounted in thecombustion chambers in such a manner as to be offset from the axis ofthe housing.

INDUSTRIAL APPLICABILITY

[0169] The gas generator of the present invention enables the airbag tobe smoothly expanded and inflated instantaneously by the gas uniformlydischarged from all around the housing without any partial expansion andinflation, thus enabling the airbag to serve its original function.

1. A gas generator, comprising: a cylindrical housing; gas generantspacked in the housing to generate gas by combustion; a plurality ofignitor devices for spouting flames into the housing to burn the gasgenerants packed in the housing, at least one of the ignitor devices iseccentrically disposed with respect to an axis of the housing; and theenhancer devices for allowing the flame of the ignitor device disposedon the eccentric position to be propagated circumferentially andradially of the housing.
 2. A gas generator, comprising: a cylindricalhousing; gas generants packed in a plurality of combustion chamberspartitioned in the housing to generate gas by combustion; a plurality ofignitor devices for spouting flames into the plurality of combustionchambers respectively to burn the gas generants packed in the pluralityof combustion chambers respectively, at least one of the ignitor devicesis eccentrically disposed with respect to an axis of the housing; andthe enhancer devices for allowing the flame of the ignitor devicedisposed on the eccentric position to be propagated circumferentiallyand radially of the housing.
 3. The gas generator according to claim 2,wherein; the enhancer devices are respectively provided in the pluralityof combustion chambers so as to extend circumferentially and radially ofthe housing, the enhancer devices are respectively in direct or indirectcontact with the gas generants in the combustion chambers and, theenhancer devices are disposed so as to be respectively ignited by theflames spouted from the ignitor devices.
 4. The gas generator accordingto claim 3, wherein; the enhancer device comprises an enhancing spaceopening in the combustion chamber and extending circumferentially andradially of the housing, the flames from the ignitor device to bespouted thereinto.
 5. The gas generator according to claim 4, wherein;the enhancing space is closed by a cushioning member; and the cushioningmember has a plurality of enhancing holes.
 6. The gas generatoraccording to claim 1 or 2, wherein; the enhancer device comprisesenhancer agent containing auto-ignition explosive composition.
 7. A gasgenerator, comprising; a cylindrical housing; gas generants packed inthe housing to generate gas by combustion; an ignitor device forspouting flames into the housing to burn the gas generants packed in thehousing; and enhancer devices for allowing the flames from the ignitordevice to be propagated circumferentially and radially of the housing.8. A gas generator, comprising; a cylindrical housing; gas generantspacked in combustion chambers partitioned in the housing to generate gasby combustion; an ignitor device for spouting flames into the combustionchambers to burn the gas generants packed in the combustion chambers;and enhancer devices for allowing the flames from the ignitor devices tobe propagated circumferentially and radially of the combustion chambers.9. The gas generator according to claim 7 or 8, wherein; the ignitordevice is eccentrically disposed with respect to an axis of the housing.10. The gas generator according to claim 7 or 8, wherein; the enhancerdevice comprises enhancer agent containing auto-ignition explosivecomposition.